The present invention pertains to a food patty molding machine and, more particularly, to an improved drive assembly and control system for such a machine.
Machines for the high volume production of molded food patties are well known in the art. Such machines are used typically to form hamburger patties from a supply of ground beef by forcing the ground beef under pressure into a multi-cavity mold plate which is rapidly shuttled on a linear slide between a fill position and a discharge position in which vertically reciprocable knock-outs push the patties from the mold cavities. U.S. Pat. No. 3,887,964 discloses the basic construction of a food patty molding machine which is basically unchanged and remains in current use. The machine disclosed in that patent utilizes a variable speed motor-driven reducer which operates a rotary crank mechanism and cooperating mechanical linkage which converts the rotary motion to reciprocable motion to drive the mold plate between its fill and discharge positions. The mechanical linkage includes a hydraulically buffered lost motion mechanism which is utilized to provide a short dwell in each of the mold plate fill and discharge positions. The variable speed drive is also mechanically linked to the knock-outs for discharging the patties from the mold plate in a manner which times operation of the knock-outs directly and mechanically to the reciprocable operation of the mold plate.
A number of disadvantages have been found to be attendant to the construction and operation of the above described food patty molding machine. The mechanical drive linkage includes a significant number of individual components resulting in a rather complex mechanism. An offset connection of the lost motion drive mechanism to the ends of the mold plate carriage results inherently in the imposition of significant laterally directed loads on the carriage slide mechanism. These lateral loads, in turn, have been found to cause substantial rapid wear to the linear drive shafts and supporting linear bearings which comprise the reciprocating carriage. Excessive wear can eventually lead to misalignment beyond the range of attainable adjustment, fracture of mold plates, and other potential damage if not closely monitored. At best, rapid wear of the mold plate carriage linear drives and bearings creates a chronic maintenance and replacement part problem. Also, the lost motion drive which is utilized to provide short dwell periods at the ends of the fill and discharge positions, is not easily adjustable to compensate, for example, for changes in temperature of the supply of ground meat or ground food product. Furthermore, because operation of the mold plate and the knock-outs is linked mechanically, there is no possibility of halting operation of one or the other of the subsystems in the event of a problem, such as misalignment of the mold plate with the knock-out cups in the discharge position. In addition, because of the strict requirements imposed on machinery used in the processing of food for human consumption, the applicable regulations require rigorous cleaning procedures, in particular high pressure washing with water. Prior art machines have not been very tolerant to high pressure washing and, as a result, periodic washing often results in shorted electric motors and other electric components, rust and corrosion, loss of lubricant from grease fittings, all adding considerably to the time and cost of maintenance and repair.